In the field of consumer automobiles, vehicle access technology has improved, making it more convenient for consumers to lock, unlock, and start their vehicles. Physical keys can be replaced with remotes, which can in turn be replaced with key fobs capable of wirelessly enabling buttons on the interior and exterior of the vehicle to perform the functions of physical keys, for example. In some examples, consumers can control vehicle locks and doors, activate a car alarm, and start the vehicle remotely, sometimes without touching a dedicated key, remote, or fob. To share access to a vehicle with another person, a primary operator can give that person the vehicle's associated key, remote, or fob. For situations where lending a key, remote, or fob is inconvenient or impractical, there exists a need in the field of consumer automobiles for a method of securely sharing vehicle access via a mobile device in the absence of a physical key, remote, or fob.